The present invention relates to a neutron detector which can be effectively used for instance in the field of a neutron scattering experiment in which a neutron source which uses a nuclear reactor or a particle accelerator, etc. or various nuclear security.
A cylinder type 3He gas proportional counter or a position-sensitive 3He gas proportional counter has been chiefly used as a neutron detector so far.
Especially, a position-sensitive 3He gas proportional detector which has been used as a one-dimensional detector has great advantages that the position of incidence of a neutron can be obtained easily by giving resistance to a core wire by which signals are collected, measuring the signals at both ends of the core wire and processing the signals, and neutron detection efficiency can be improved by increasing the pressure of 3He gas. And, the sensitivity of gamma rays which form the background is low. In addition, this counter tube was indispensable in a neutron scattering experimental apparatus which had to arrange the one-dimensional neutron detector in a vacuum tank, because it has simple construction and excellent vacuum-proof.
On the other hand, 3He gas multi-wire two-dimensional neutron detector etc. have been used as a neutron image detector used in the neutron scattering experimental apparatus which does not need the vacuum-proof.
Moreover, the detector which detects a one-dimensional or a two-dimensional neutron image by coding the position of incidence of the fluorescence emitted from 6Li glass scintillator or ZnS/6LiF half transparent type neutron scintillator, etc. by using optical fibers or wavelength shift fibers, and detecting it by a photomultiplier tube has been used as a neutron image detector with a scintillator. In addition, as radiation detectors other than the neutron detector which adopts the scintillator or the wavelength shift fiber, the following radiation detectors have been used, that is, (1) a radiation detector comprised of a combination of a liquid He scintillator, a TPB wavelength converter and one coiled wavelength shift fiber, (2) a radiation detector comprised of a combination of a plastic scintillator and a ring wavelength shift fiber, and (3) a radiation detector comprised of a combination of a cylindrical scintillator and a wavelength shift fiber built therein.
In these detectors, the fluorescence emitted from an only transparent scintillator is finally collected to one place by using wavelength shift fibers, and the signal processing is carried out by one optical detector to detect the radiation. Accordingly, it was very difficult to apply such a radiation detection method in which these wavelength shift fibers are used to the neutron detector requiring a high detection efficiency in which the ZnS/6LiF half transparent type neutron scintillator, etc. are used and the sensitivity of gamma rays which form the background have to be reduced.    [PATENT DOCUMENT 1] JP2000-187077A    [PATENT DOCUMENT 2] JP2002-071816A    [PATENT DOCUMENT 3] JP2011-141239A    [PATENT DOCUMENT 4] JP2000-065937A    [NON-PATENT LITERATURE 1] Nucl. Instr. and Meth., A430(1999)311-320    [NON-PATENT LITERATURE 2] Nucl. Instr. and Meth., A516(2004)475-485    [NON-PATENT LITERATURE 3] Nucl. Instr. and Meth., A539(2005)172-176